GSTM1 and hydrops fetalis: ANOVA showed significant differences in the NT-proBNP levels (F = 48.5, p < 0.001), MoM-Hb values (F = 81.62, p < 0.001) and MoM-MCA-PSV values (F = 68.81, p < 0.001), comparing controls and subjects, subgroups of fetuses with PVB19 infection and fetuses with Rhesus incompatibility as well as fetuses with and without hydrops fetalis in the fetal blood before the start of therapy, compared to the controls at the time of fetocide (see Fig. 3).